42 



SYNOPSIS OF AMERICAN FOSSIL BRACHIOPODA. 

 Table Y. — Silitiian Bracliiopoda — Coutinued. 



[BULL. 87. 



Species. 



Zygospira ( ?) minima Hall 



Zygospira ( ?) paupera Billings 



Number of Silnrian species, 311. 



Number of species in each division 



Number of species common to the Medina and the other 

 divisions 



Number of species common to the Clinton and the other 

 divisions 



Number of species common to the Niagara and the other 

 divisions 



Number of species common to the Neosilurian and the other 

 divisions 



Species common to the Silurian and Devonian systems, 5. 



Number of species passing from each division into the De- 

 vonian 



Eo- 

 silurian. 



Mesosilurian. 



Medina. 



Anti- 



costi, 



Clinton. 



116 



19 



Guelph, 

 Arisaig, 

 Niagara. 



N 



195 







19 



Neosi- 

 lurian. 



Tentac- 

 ulito. 



Water- 

 lime. 



17 

 

 

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